Multi-layer microvalve having integral closure, membrane and pressure compensating surface forming a middle layer

ABSTRACT

The microvalve according to the invention is composed in a layered manner of at least one bottom part (11), one middle part (12) and one top part (13). The sealing ring (31) (closure member), the valve plate (29) (pressure-compensating surface) and the membrane (26) are integrated in the middle part (12), this integral component being manufactured by a plastic moulding process. The actuation of the valve takes place using an electrical operating apparatus, for example by an electrostatic drive, an electromagnetic or a piezoelectric drive. In particular in the case of the electrostatic drive, two electrodes (17, 22) are applied in a layered manner to the middle part (12) or the bottom part (11). The bottom part, middle part and top part are joined together and connected, for example bonded or welded, permanently to one another.

BACKGROUND OF THE INVENTION Prior Art

The invention starts from a microvalve of layers arranged one above theother and connected to one another and relates furthermore to a valvearrangement having at least two microvalves connected in parallel.

Microvalves of this type are usually composed of semiconductor layerswhich are bonded to form the permanent connection. The individualsemiconductor layers are brought into the shape and structure necessaryfor the function by complex etching methods. A microvalve of this typeis described, for example, in WO 90/15933. Such microvalves arerelatively expensive due to the expensive layer material or the complexmanufacturing processes. Owing to the very complex production technique,the valves have to be produced in very large numbers in order to achievea sufficient cost-effectiveness. Adaptations or differentiations ofthese microvalves during manufacture can only be carried out atconsiderable expense.

SUMMARY OF THE INVENTION

The microvalve according to the invention is characterized in that theclosure member, the membrane and the pressure-compensating surface areformed in an integral plastic component which is a middle layer of themicrovalve.

The microvalve according to the invention therefore is distinguished bya simple construction and can thus be manufactured cost-effectively. Theconstruction is selected such that the valve can be composed with a verysmall number of individual elements so that the connection methods arereduced to a minimum and the errors and complexities associated withthese connection methods are thus likewise reduced.

In the manufacture of the valve, the middle part, in particular, ismanufactured by a plastic moulding process--in particular injectionmoulding or embossing--and thus by a moulding or structuring processwhich has a high degree of precision and reproducibility with lowexpense. Modifications and adaptations are possible with relativelylittle expense due to modular construction of one or more valves.

In this manufacturing method, differentiated requirements in respect ofthe material or different material components, compositions or types oflayering can additionally be fulfilled.

The valve arrangement according to the embodiment in which the twoelectrodes of the electra static device are designed at least as part ofthe outer surface of a pyramid, has the advantage that adaptations ofthe flow volume can easily be undertaken due to the modular constructionand the parallel connection of a plurality of microvalves. The valvearrangement can be adapted in a simple manner to different volumerequirements. By means of different fitting in the type and number ofthe microvalve units, a diversity of variants can additionally beachieved with little diversity of components in a simple andcost-effective manner in terms of production.

Further advantages and advantageous further developments result from thedescription and the subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail with reference to thefollowing description and drawing. The latter shows,

in FIG. 1, a section through a microvalve according to the invention ina simplified illustration,

in FIG. 2, a section through a second exemplary embodiment of themicrovalve,

in FIG. 3, a detail of this second exemplary embodiment,

in FIGS. 4 and 5, a third and fourth exemplary embodiment,

in FIG. 6, in the left half of the picture a first modification and inthe right half of the picture a second modification of the microvalveaccording to FIG. 5,

in FIG. 6a, a plan view of the opened first modification,

in FIG. 7, in the left half and right half of the picture in each casedifferent modifications of the microvalve according to FIG. 1,

in FIGS. 8 and 9, in their left and right halves of the picture in eachcase further modifications of the micro-valve according to FIG. 1,

in FIG. 10, a cutaway, perspective illustration of a microvalvearrangement with microvalves connected in parallel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The microvalve 10 illustrated in FIG. 1 is joined together from threecomponents placed one on the other in a layered manner, a bottom part11, a middle part 12 and a top part 13. The bottom part 11 consists of aplastic material or of aluminium and is designed as a cylindrical disc.In the axial direction, it is penetrated by two continuous channels 14,15 which serve to supply pressure medium. However, it is also possibleto allow the supply of pressure medium to take place via a single or viaa plurality of channels. An electrically conducting layer 17 is appliedto the upper side 16 of the bottom part 11, which layer 17, in turn, iscovered by an insulating layer 18. If the bottom part 11 is producedfrom an electrically conducting material, an additional insulatinglayer--not illustrated here--is arranged between the electricallyconducting layer 17 and the bottom part.

The middle part 12 has a cylindrical base plate 20 whose dimensionscorrespond to those of the bottom part 11 and which is placed on thelatter. Applied to the underside 21 of the base plate 20 is anelectrically conducting layer 22 which, in the assembled state of themicrovalve 10, is separated from the electrically conducting layer 17 ofthe bottom part 11 by the insulating layer 18. The bottom part 11 andmiddle part 12 are firmly and permanently connected to one another bybonding or welding. In this case, the electrically conducting layers 17and 22 are connected in a manner not illustrated to feed lines which canbe connected to a voltage source via switching devices.

The base plate 20 of the middle part 12 likewise has two channels 23, 24which are flush with the channels 14, 15 of the bottom part 11. In amodified design of the bottom part 11, these channels are adaptedappropriately. Recessed into the underside 21 of the middle part 12 is aflat, cylindrical depression 25 whose diameter is smaller than thedistance between the channels 23, 24. The depression 25 is likewisecovered by the electrically conducting layer 22 and is dimensioned insuch a way that the base plate 20 is designed in this region as amembrane 26. However, the depression 25 can also have a differentcross-sectional shape from that of a circle, for example that of asquare or of a hexagon, and it is advantageously integrallyaxisymmetrical. The top part 13, the base plate 20 and the bottom part11, too, can not only be of cylindrical, but also of correspondinglyaxisymmetrical design.

Formed on the upper side 27 of the base plate 20 is a cylindrical(axisymmetrical) projection 28 whose dimensions are smaller than thoseof the depression 25. This projection 28 widens on the side opposite thebase plate 20 into a flat, frustoconical valve plate 29. The latter has,on its free end face 30, an annular sealing ring 31 which serves as aclosure member of the microvalve.

The annular edge 33 of the cup-shaped top part 13 is placed on the upperside 27 of the base plate 20. The interior 34 of the top part 13 isdimensioned such that its diameter is greater than the distance betweenthe channels 23, 24. The height of the interior 34 is dimensioned suchthat the sealing ring 31 bears against the inner side 35 of the basepart 37 of the top part 13. The base part 37 is penetrated by an outletchannel 38 which opens out into the interior 34 within the region 40bounded by the sealing ring 31. This region 40, bounded by the sealingring 31, of the top part 13 serves as a valve seat which interacts withthe sealing ring 31 serving as a closure member. A nozzle plate 39 isfitted into the outlet channel 38 to influence the flow characteristicsof the pressure medium. However, this nozzle plate can also beintegrated.

The microvalve 10 described is suitable for many applications, forexample as a fuel injection valve in internal combustion engines ofmotor vehicles. The interior 34 communicates with a source of pressuremedium--for example a fuel line--via the channels 14 and 15 in thebottom part 11 and the channels 23, 24 in the middle part 12. In theswitching state illustrated, the interior 34 is closed on one side, i.e.the sealing ring 31 of the valve plate 29 serving as a closure memberbears against the inner side 35 of the top part 13 or of the base part37 and closes the outlet channel 38 (valve seat). The prestress or theforce with which the valve plate 29 or the sealing ring 31 is pressedagainst the inner side 35 of the top part 13 is dependent on the elasticproperties of the material of the middle part or on the design of themembrane 26 and on the ratio of the height of the interior to thecorresponding dimensions of the projection 28 and the valve plate 29together with the sealing ring 31. In this case, the membrane 26 acts,due to the design and arrangement of the projection 28, as an annularmembrane and serves as a spring means which, in the neutral switchingstate of the microvalve, presses the closure member (sealing ring 31)against the valve seat (inner side 35 around the outlet channel 38).

If the two electrically conducting layers 17, 22 are connected to thevoltage source via the feed lines (not illustrated), the switchingdevices and the corresponding connections in such a way that the twolayers have opposite polarity, the latter act as a capacitor and, in theregion of the depression 25, as an actuating means for the microvalve.Owing to the forces of attraction due to the different poling of the twolayers (electrodes of an electrostatic drive), the membrane 26 curvesdown towards the bottom part 11 in the region of the depression 25. Bymeans of the connection of the valve plate 29 via the projection 28 tothe membrane 26, the sealing ring 31 lifts off from the inner side 35 ofthe top part 13, thus producing a connection from the interior 34 to theoutlet channel 38. In the case of excessive deflection of the membrane26, the insulating layer 18 prevents contact of the two electricallyconducting layers 17, 22 (electrodes of the electrostatic drive) andthus prevents a short circuit.

An even lifting-off from the inner side 35 or an even bearing againstsaid inner side is guaranteed due to the rotationally symmetrical oraxisymmetrical design of the depression 25, the membrane 26, theprojection 28 and the valve plate 29. When the outlet channel 38 isclosed, the pressure in the interior 34 acts, on the one hand, downwardsonto the membrane 26 and, at the same time, onto the free annularsurface of the valve plate 29. The two annular surfaces, i.e. theannular surface of the membrane 26 and the annular surface acted upon bypressure on one side (resulting annular surface of the valve plate 29)are matched to one another in their dimensions in such a way that themovable construction element (valve plate 29, projection 28, membrane26) is statically pressure-compensated. The upwardly directed forces andmoments due to the pressure on the resulting annular surface on thevalve plate 29 and those directed downwards onto the correspondingannular surface of the membrane 26 are equal in size. In this case, theeffective annular surface on the valve plate 29 acts as apressure-compensating surface relative to the membrane 26. In this case,it is assumed that the pressures below and above the movableconstruction element are essentially equal in size, i.e. the pressure inthe depression 25 should correspond essentially to the pressure in theoutlet channel 38 when the valve member is closed. However, there doesnot inevitably have to be the same medium in the depression 25 as in theoutlet channel 38. Owing to the pressure-compensated construction of themicrovalve 10, the restoring force due to the membrane 26 can be verysmall. Owing to the pressure-compensated construction, it is furthermorepossible for very high pressures to be controlled and for a relativelyweak drive to be usable as the electrical actuating means. Themicrovalve 10 is suitable for controlling great hydraulic or pneumaticcapacities and allows a high degree of dynamics. An only partialpressure compensation can also be achieved by appropriate modificationof the effective annular surface on the valve plate 29(pressure-compensating surface) relative to the surface of the valveplate 29 subjected to outlet pressure in the region of the outletchannel 38. By this means, however, consideration of the dynamic flowforces is possible at the same time so that the switchingcharacteristics of the microvalve 10 can be influenced.

In the microvalve 10 described here, the middle part 12 is manufacturedby injection moulding from a plastic whose composition and structure areadapted to the application site and the pressure medium. It is alsopossible to produce the middle part 12 and/or top part 13 and bottompart 11 by embossing. The frustoconical design of the valve plate 29, inparticular, facilitates the demoulding of the middle part 12 afterinjection moulding. After demoulding and any burring, the underside(including the depression 25 and membrane 26) is provided with anelectrically conducting layer 22 and contact is made with it. Owing tothe design described, the essential construction elements are integratedin the middle part 12 with narrowly tolerated dimensions. The height ofthe interior 34--as a further dimension essential to the function--isprimarily responsible for a good bearing of the sealing ring 31 and theprestress of the membrane 26.

In two process steps, the bottom part 11, which can be produced byinjection-moulding, embossing or stamping likewise from a plastic orfrom aluminium, is firstly provided with an electrically conductingcoating on its upper side 16 and contact is made with it, andsubsequently the said bottom part 11 is provided with the insulatinglayer. When aluminium is used, a further insulating layer must firstlybe applied. The plastic for the bottom part 11 can be a different onefrom that of the middle part 12 since the elastic properties are not ofprimary importance. Instead, other properties, such as heat-resistance,strength, or the like, can be of primary importance. The bottom part 11and middle part 12 are joined together in the correct position in afurther operation and bonded or welded to one another. In addition to asuitable plastic, the use--as already mentioned--of a metal material(e.g. aluminium) which is adapted in terms of its thermal expansion isalso possible. It is also possible to make the channels 14, 15 or 23, 24by boring, laser-cutting or similar methods after this joining-togetherso that the assignment in the correct position is always guaranteed.

The top part 13 can be made up of a plastic which differs from that ofthe bottom part 11 or of the middle part 12 or from both. The top part13 is manufactured by a corresponding moulding process from firmplastic, for example by embossing, or from a free-flowing plastic byinjection-moulding. The top part 13 can also consist of a suitable metalor a (metal) alloy. After the moulding operation, the nozzle plate 39 isinserted into the outlet channel 38 and bonded or welded. In the case ofinjection-moulded or injection-embossed top parts, the nozzle plate canalso be produced in one piece with said top parts. The top part 13 isplaced on the middle part 12 and likewise bonded or welded. It is alsopossible to join and connect the bottom part 11, middle part 12 and toppart 13 in a common operation. The top part 13 and/or the bottom part 11can also already be adapted to the application site of the microvalve inthe moulding process, for example by moulding on tube connections,attachment means or safeguards against rotation. In contrast to theelectrostatic valve actuation described, the coating on the bottom partand middle part can also be replaced by a piezoelectric coating on themiddle part so that the actuation of the valve takes place in a mannerknown per se by means of the change in shape due to the piezoelectriceffect.

FIGS. 2 and 3 describe a second exemplary embodiment of a microvalveaccording to the invention, the same reference numerals being used forthe same construction elements.

The microvalve 10a differs from that described above mainly due to thedesign of the depression and thus of the membrane, thus resulting inhigher drive or actuation forces. The depression 25a in the base plate20a of the middle part 12a has the shape of a flat truncated cone whichwidens towards the underside. Starting from this truncated cone is acentral blind bore 41 which protrudes through the projection 28 rightinto the valve plate 29. The underside 21 of the base plate 20 and thedepression 25a --as in the exemplary embodiment above--are provided withan electrically conducting layer 22. Correspondingly, the bottom part 11is provided with an electrically conducting layer 17 and an insulatinglayer 18.

The base plate 20a is not designed as a flat disc as in the exemplaryembodiment above, but has, in the region of the membrane 26a, an upwardslope 42 which corresponds to the conical course of the depression 25a,thus guaranteeing an even membrane thickness.

In the electrostatic actuation of the microvalve 10a, the membrane 26abears against the bottom part 11a starting from the outer circumferenceof the depression 25a towards the centre since the forces of attractionincrease quadratically with the reciprocal value of the distance betweenthe electrically conducting layers. In this case, the displaced (gas)volume can escape into the blind bore 41 in the case of a small pressureincrease.

FIG. 4 illustrates a third exemplary embodiment of the microvalve inwhich a complete, static pressure compensation of the moved constructionelements is possible at any outlet pressure. The microvalve 10bcorresponds in its construction essentially to the microvalve 10described in FIG. 1, a base part 44 being attached additionally to thebottom part 11b. On its underside 45, the bottom part 11b has radialchannels or--as illustrated here--a circumferential annular groove 46which extends from the channels 14, 15 up to the outer edge. By means ofthis annular groove 46, the channels 14, 15 can be acted upon bypressure medium from the outer circumference of the microvalve 10b.Arranged furthermore in the bottom part 11b is a central bore 47 whichstarts from the underside 45 and protrudes into the depression 25. Thebase part 44 is produced from plastic by a moulding process as a flat,cylindrical (axisymmetrical) disc and has two cylindrical(axisymmetrical) depressions 48, 49 in its upper side 50 and underside51 respectively. The depressions 48, 49 form a second membrane 52 in thebase part 44.

The base part 44 is attached either in a separate operation or togetherwith other components (top part, middle part, bottom part) and isconnected, for example bonded or welded, firmly and non-releasably tothe bottom part 11b.

When the microvalve 10b is operated, the underside 51 of the base part44 is acted upon by the outlet pressure (P_(out)) which also prevails inthe outlet channel 38. The movable element (valve plate 29, projection28, membrane 26) is thus always completely (statically)pressure-compensated independently of the magnitude of this outletpressure.

FIG. 5 describes a fourth exemplary embodiment of the microvalve inwhich the actuating means or the drive is of electromagnetic design.This actuating means consists of a pot magnet which is integrated in thebottom part, is excited by a coil and has a low-retentivity core. Thetop part 13c and middle part 12c of the microvalve 10c are essentiallyconstructed in the same manner as the corresponding components in themicrovalve 10 described in FIG. 1. In contrast thereto, however, theelectrically conducting layer is omitted in the middle part 12c.Instead, ferromagnetic particles are embedded in the plastic, whichparticles are introduced into the raw moulding compound during thepreparation thereof.

The electrically conducting layer and the insulating layer are likewiseomitted in the bottom part 11c. Instead, the bottom part has athrough-bore 55 into which a core 56 of stacked electroplates which areknown per se is firmly inserted. This core 56 has, on its end facefacing the middle part 12c, an annular groove 57 into which a coil 58,known per se, is wound.

By appropriate current supply to the coil 58, the projection 28 and thevalve plate 29 of the middle part 12c are attracted towards the coil 58and act as magnet armatures. The depression 25 or the gap between thecoil 58 and the base of the depression 25 acts as an operating air gap.In this case, the flow of the magnetic circuit is guided essentiallythrough the projection 28.

It is also possible to restrict the embedding of ferromagnetic particlesin the middle part 12c locally, said particles then only being embeddedin the region of the magnetic flow.

In order to facilitate the winding of the coil 58, the core 56 can alsoconsist of two concentric parts inserted one inside the other, an outersleeve and an inner winding cylinder. Instead of the design of the core56 of stacked electroplates, said core can also be moulded from aplastic which is mixed with ferromagnetic particles.

FIG. 6 shows in the left half and the right half of the picture in eachcase a modification of the microvalve described above, whichmodifications differ from the latter by a changed course of the magneticflow. The two embodiments themselves differ in the design of the guidering and of the corresponding shaping of the top part, the air gapbetween the guide ring and the valve plate being arranged either lyingin the power flux (direction of movement of the valve plate) ororthogonally thereto. In both cases, the bottom part 11d or 11e has inits upper side an annular groove 60 whose outside diameter correspondsapproximately to that of the depression 25. The coil 58 is wound intothis annular groove 60. The bottom part 11d or 11e is mixed withferromagnetic particles and is either--as illustrated--of integraldesign or--as described for the core 56--composed of two concentricparts. Placed on this bottom part 11d or 11e is the middle part 12d or12e which corresponds in its design essentially to the middle part 12cdescribed above.

In the case of the first modification of the microvalve--illustrated inthe left half of the picture--a ferromagnetic guide ring 61 is placed onthe base plate 20d of the middle part 12d, the outer dimensions of saidguide ring corresponding to those of the base plate 20d and the innerdimensions thereof being slightly larger than the dimensions of thevalve plate 29d or of the depression 25. FIG. 6a shows this guide ringin a plan view of an opened microvalve 10d. In the region of thechannels 23d and 24d, this guide ring has, on its underside 63, a groove62 starting from the inner circumference. Furthermore, it has, on itsupper side, at least two bores or cut-outs 66 which are arranged in sucha way that they guide the flow volume of the fluid past the sealing ring31 when the valve is open. The gap between the guide ring 61 and thevalve plate 29 can then be kept small for the effective guiding of themagnetic flow. The thickness of the guide ring 61 corresponds to theheight of the edge 33 of the top part 13 in the exemplary embodimentsdescribed above, i.e. the thickness of the guide ring 61 is selectedsuch that the sealing ring 31 of the valve plate 29d is pressed againstthe top part 13d with a defined pressing-on force. In this modification,the top part 13d is consequently designed as a flat disc (without asleeve-shaped edge).

The middle part 12d, together with the base plate 20d, projection 28 andvalve plate 29d, is preferably, like the guide ring 61, moulded from aplastic which is mixed with ferromagnetic particles.

The joining-together and connecting of the individual layer components(bottom part, middle part, guide ring, top part) can take place inindividual process steps or in any combination in analogy to theembodiments described above.

In the microvalve 10d, the magnetic circuit runs through the depression25 as an operating air gap, the projection 28, the valve plate 29d, theannular space between the valve plate 29d and the guide ring 61(subsidiary air gap) and the base plate 20d, and is closed by means ofthe bottom part 11d. In this case, the subsidiary air gap liesorthogonally relative to the direction of movement of the valve plate29d.

In the second modification (right half of the picture), the subsidiaryair gap lies in the direction of force so that the attracting forces areintensified to a certain degree.

As in the embodiment above, the guide ring 61e is placed on the baseplate 20e; its inner dimensions correspond approximately to thedimensions of the depression 25. However, its thickness is smaller thanin the previous embodiment and is smaller than the distance between thebase plate 20e and the valve plate 29e at the outer edge thereof. In theregion of the channels 23e, 24e, the guide ring 61e has passages 64which are flush with said channels. To improve the magnetic flow, thevalve plate 29e is designed with a greater outer dimension so that itpartially covers the guide ring 61e. The dimensions of the sealing ring31 and those of the depression 25, however, remain unchanged or areadapted to one another in respect of the pressure compensation.

In the region of the covering of the valve plate 29e and the guide ring61e, the latter has a conical recess 65 whose slant is adapted to theconical course of the valve plate 29e.

The top part 13e has a sleeve-shaped edge 33e which rests on the guidering 61e, and whose height is selected such that the valve plate 29e orthe sealing ring 31 bears against the inner side 35e of the top part13e.

In this embodiment, too, the middle part 12e, the guide ring 61e and thebottom part 11e are ferromagnetic. The magnetic circuit runs in analogyto the exemplary embodiment described above, with the difference thathere the annular gap between the guide ring 61e and the valve plate 29e(subsidiary air gap) is flowed through in the direction of movement ofthe valve plate 29e.

In order to prevent the negative consequences of possibly occurringcreep of the membrane 26, the latter can alternatively be designed as apure sealing membrane without spring effect. Alternatively oradditionally, the design of the depression or of the membrane and thatof the bottom part can be varied in the region of the depression. Inthis respect, two possible embodiments are illustrated in FIG. 7. Here,both embodiments are explained with reference to the electrostaticactuation principle, but this can readily be transferred to thepiezoelectric or electromagnetic principle.

In order to restrict the action of the membrane 26f or 26g to a puresealing function, additional spring elements 67 are provided both in themicrovalve 10f--illustrated in the left half of the picture--and in themicrovalve 10g--illustrated in the right half of the picture. These aredesigned as radially extending spring beams which are in each casefirmly connected to the sleeve-shaped edge 33f, 33g on the one hand andto the outer edge of the valve plate 29f, 29g on the other hand.

The spring elements 67 are also moulded on during the moulding processof the sleeve-shaped edge 33f, 33g and of the valve plate 29f, 29g, andare produced simultaneously with these parts in one injection-mouldingitem. For this purpose, the middle part 12f, 12g is advantageously giventhe construction described in the following. The base plate 20f, 20g andthe projection 28f, 28g are produced as one component on which the valveplate 29f, 29g with the spring elements 67 and the sleeve-shaped edge33f, 33g are placed and bonded or welded. The top part 13f, 13g is thenonly a disc.

In this case, the edge 33f, 33g, together with the base plate 20f, 20g,forms the middle layer of the microvalve 10f, 10g.

An influence of creep of the membrane in the radial direction on amovement in the axial direction (opening and closing direction) can alsobe reduced by a corresponding design of the membrane, as is illustratedin FIG. 7. By corresponding shaping and/or expansion, the membrane 26fis given a curved cross-section or an approximately S-shapedcross-section (26g). Owing to these or other curves or bends of themembrane 26f, 26g, the effects of a change in shape of the membrane inthe transverse direction (perpendicular to the direction of movement ofthe valve plate) on the pressing-on force or prestress are substantiallyreduced.

In the microvalve 10f, a circumferential annular groove 68 isadditionally formed in the bottom part 10f in the region of the membrane26f so that contacting or bearing of the membrane is avoided even athigh pressure differences on its two sides.

Each of the measures illustrated here in FIG. 7 to reduce the effect ofany membrane creep can be applied separately, with one or both of theother methods or designs to the microvalves according to FIG. 1, 4 to 6.In the microvalve 10a according to FIG. 2, the membrane 26a isadvantageously adapted, for example by targeted inclusion of fibrousmaterials, metals or by using correspondingly creep-resistant plastics.In this valve, high actuating forces or large valve strokes can bebrought about above all by the use of the electrostatic drive principleso that the controllable flow volume and/or the operating pressure canbe increased.

The modifications (10h, 10i, 10k, 10l) of the microvalve 10 described inFIGS. 8 and 9 differ from that described in FIG. 1 by alterations in thebottom parts (11h-11l) and the middle parts (12h-12l).

The bottom parts 11h and 11k illustrated in the respective left halvesof the picture of FIG. 8 and FIG. 9 respectively have a conicaldepression 71h, 71k starting from the upper side 16h and 16k,respectively, of said bottom parts. The bottom parts 11i and 11lillustrated in the respective right halves of the picture of FIG. 8 andFIG. 9 respectively have a frustoconical depression 71i and 71l startingfrom the upper side 16i and 16l, respectively, of said bottom parts.Each of these depressions 71h to 71l can, however, also be designed asan (axisymmetrical) pyramid-shaped or truncated pyramid-shapeddepression.

The outer surfaces of the depressions 71h, 71k and the outer surfaces ofthe depressions 71i, 71l together with the end faces 72i, 72l areprovided with an electrically conducting layer 17h or 17l respectively.

The middle parts 12h and 12i illustrated in FIG. 8 have in each case aprojection 28h and 28i and a valve plate 29h and 29i which correspond tothose of the microvalve 10 in FIG. 1 and are arranged on a base plate20h or 20i. The latter has, on its underside 21h or 21i, a depression25h or 25i which is of annular design and whose outside diameter isgreater than the opposite outside diameter of the depression 71h or 71i.

The inside diameter corresponds approximately to that of the projection28h or 28i. By means of the depression, the membrane 26h, 26i isformed--in analogy to the exemplary embodiment according to FIG. 1.Starting from the underside 21h or 21i, there is formed on the undersideof the membrane or of the base plate a conical projection 73h or afrustoconical projection 73i which protrudes into the depression 71h or71i without the respective outer surfaces contacting one another. Thecone angles of the depression 71h or 71i and the projection 73h or 73icorrespond to one another. If the depressions 71h-71i are ofpyramid-shaped or truncated pyramid-shaped design, the projections73h-73i are adapted correspondingly.

The depressions 25h and 25i, the outer surfaces of the projections 73hand 73i and the underside 74i of the projections 73i are provided withan electrically conducting layer 22h and 22i respectively.

In analogy to the exemplary embodiment according to FIG. 1, aninsulating layer (not illustrated in detail here) can be applied to theelectrical layer 17h or 17i of the bottom part or to the electricallyconducting layer 22h or 22i of the middle part. The two electricallyconducting layers 17h or 17i and 22h or 22e act--as already describedabove--as electrodes of an electrostatic drive. The surface of the twoelectrodes is enlarged by the shaping thereof. With the same radius andthe same stroke of the electrodes relative to those of the exemplaryembodiment according to FIG. 1, the electrostatic driving force isconsiderably greater than that of an electrostatic drive with flatelectrodes. If, in contrast, a driving force of equal size is to begenerated, a correspondingly greater working stroke can be implemented.The cone angle or pyramid angle can assume any values between 0°(infinitely flat cone) to 90° (infinitely pointed cone). The size of thecone angle and the height of the truncated cone are dependent on therequirements placed on the microvalve and the possibilities of theproduction process, and they are restricted by the sensitivity of theclosure element (valve plate with projection) to tilting.

The modifications of the exemplary embodiment described in FIG. 9 differfrom that described above in FIG. 8 by a changed position of themembrane 25k or 25l. The diameter of the conical or frustoconicaldepression 71k or 71l corresponds on the upper side 16k or 16l of thebottom part to the outside diameter of the membrane. The membrane 26k or26l runs together with the outer surface of the projection 73k or 73lparallel to the outer surface of the depression 71k or 71l. Theprojection 28k or 28i between the base plate 20k or 20i and the valveplate 29k or 29l is adapted to the correspondingly changed dimensions,i.e. a conical transition piece 74k or 74l is fitted between theprojection and the valve plate.

In contrast to the four embodiments or modifications of the microvalvedescribed, the electrodes can assume any other geometry which issuitable to enlarge the active surface of the drive (outer surface≧basesurface) and/or to reduce the distance between the electrodes with thesame stroke.

FIG. 10 illustrates a valve arrangement having nine individualmicrovalves 10 which are connected in parallel and of which threemicrovalves are illustrated in section. The valve arrangement is ofmodular construction and has a plate-like bottom part 80 with acollective line 81 via which the pressure medium is supplied. Theplate-like bottom part 80 corresponds in its function and itsconstruction essentially to the bottom part 10 of the microvalveaccording to FIG. 1, in this case nine individual bottom parts beingjoined together to form a common bottom part, and the individualpressure-medium channels being connected to form a collective channel.Placed on the plate-like bottom part 80 is a likewise plate-like middlepart 82 on which, in turn, a plate-like top part 83 is placed. The toppart 83 corresponds in its function and its construction to the top part13 according to FIG. 1, in each case nine top parts being joinedtogether to form a component. The top part 83 correspondingly has 9nozzle plates 39 which are arranged in three rows each consisting ofthree nozzle plates or microvalves. Each of these nozzle plates 39closes off an outlet channel 38 which starts from the interior 34. Asalready described in FIG. 1, the outlet channel 38 is closed by thevalve plate 29 of the microvalve. Each of the nine valve plates 29 witha corresponding projection 28, membrane 26 and depression 25 is formedcorrespondingly in the middle part 82. Each membrane or each depression25 is provided, on its underside, with an electrically conducting layer(not illustrated here) without the individual electrically conductinglayers contacting one another. Arranged opposite them on the bottom part80 are nine individual electrically conducting layers which can beactuated individually and independently of one another. The electricallyconducting layers 17 and the opposite electrically conducting layers inthe depressions 25 in each case form the electrostatic drive of amicrovalve.

The action of pressure on each individual microvalve takes place viaconnection channels 85 which start from the collective pressure line 81and penetrate the middle part 82 and the top part 83 into the interior34.

For the pressure compensation, each of the microvalves 10 is assigned anindividual compensation channel 86 which connects the outlet channel 38to the depression 25. The individual microvalves can also be designed insuch a way that the compensation channel acts upon the underside of amembrane 52 illustrated in FIG. 4 with the pressure of the outletchannel 38. Alternatively, the compensation channel 86 can additionallyrun through the valve plate 29 and the projection 28 and connect thecavity 88 below the slack membrane 52b with the depression 25. Pressurefluctuations in the outlet channel 38 are transmitted from the membrane52b to the cavity 88 and are passed on by the compensation channel 86 tothe underside of the drive membrane 26. All the variants of thecompensation channel, together with the membrane 52b or even without it,bring about a complete static pressure compensation. When the nozzleplate 39 is used, the pressure in the outlet channel is subjected tofluctuations whose effects can thus be compensated.

As already described, each of the microvalves 10 can be actuatedindividually and communicates in each case with the collective pressureline 81 independently of the other microvalves. The flow volume throughthe valve arrangement can thus be switched in stages from zero up to aflow volume which corresponds to the sum of the nine individual flowvolumes of the microvalves.

In contrast to the exemplary embodiment described here, different valveelements can also be arranged in the middle part 82, i.e. differentdesigns of the microvalve can be combined in the valve arrangement. Forthis purpose, different middle parts 12, 12a to 12l can then becombined, for example, to form a common middle part 82 or can beinserted into a corresponding carrier plate. The plate-like bottom part80 and the top part 83 must be adapted correspondingly. Furthermore, itwould also be possible to connect a plurality of microvalves 10, 10a toh together to form a valve arrangement, in that the individual bottomparts 11, 11a to 11l and/or the top parts 13, 13a to 13l are replaced bya corresponding common bottom part 80 or top part 83.

We claim:
 1. A microvalve, comprising a plurality of layers arranged oneabove the other and connected to one another; two pressure mediumconnections for feeding and discharging a pressure medium; a valve seatarranged between said connections; a closure member cooperating withsaid valve seat and integrated in one of said layers, said closuremember adjoining a space which is acted upon by the pressure medium andhaving a pressure-compensating surface; and a pressurized membranearranged so that said pressure compensating surface acts counter to saidpressurized membrane, said closure member, said membrane and saidpressure compensating surface being formed as a plastic component whichis a middle layer, said closure member, said membrane and said pressurecompensating surface being formed as an integral plastic component whichforms said middle layer.
 2. A microvalve as defined in claim 1; andfurther comprising electric actuating means acting on said closuremember for deflecting the latter.
 3. A microvalve as defined in claim 2;and further comprising resilient restoring means formed so that saidclosure member is lifted from said valve seat by actuating saidelectrical actuating means and is brought to rest against said valveseat again by said resilient restoring means.
 4. A microvalve as definedin claim 3, wherein said resilient restoring means is formed as saidmembrane.
 5. A microvalve as defined in claim 2, wherein said electricalactuating means is formed as an electrostatic device having twoelectrodes, one of said electrodes being formed in a layered manner atleast on an underside of said membrane.
 6. A microvalve as defined inclaim 5, wherein said plurality of layers includes a bottom layer, theother of said electrodes being applied in a layered manner to an upperside of said bottom layer.
 7. A microvalve as defined in claim 2,wherein said electrical actuating means is formed as a piezoelectriccoating provided on an underside of said membrane.
 8. A microvalve asdefined in claim 1, wherein said middle layer has an underside facingaway from said closure member, said membrane being formed by a cutout onsaid underside.
 9. A microvalve as defined in claim 8, wherein saidcutout is formed as a flat cylinder.
 10. A microvalve as defined inclaim 8, wherein said is formed as an integral axis symmetricaldepression.
 11. A microvalve as defined in claim 1, wherein said closuremember and said pressure compensating surface are formed on a valveplate.
 12. A microvalve as defined in claim 11, wherein said membranehas a surface subjecting to a pressure and an active surface acting assaid pressure-compensating surface, said surfaces being formed on saidvalve plate so that forces and moments are eliminated due to pressuresacting on said membrane and said pressure compensating surface.
 13. Amicrovalve as defined in claim 1, wherein said membrane is formed as anannular membrane.
 14. A valve arrangement, comprising at least twomicrovalves each including a plurality of layers arranged one above theother and connected to one another; two pressure medium connections forfeeding and discharging a pressure medium; a valve seat arranged betweensaid connections; a closure member cooperating with said valve seat andintegrated in one of said layers, said closure member adjoining a spacewhich is acted upon by the pressure medium and having apressure-compensating surface; and a pressurized membrane arranged sothat said pressure compensating surface acts counter to said pressurizedmembrane, said closure member, said membrane and said pressurecompensating surface being formed as a plastic component which is amiddle layer, said plurality of layers each of said microvalves having abottom layer and a top layer, said bottom layers of said microvalves andsaid top layers of said microvalves being formed as a common component,said closure member, said membrane and said pressure compensatingsurface being formed as an integral plastic component which forms saidmiddle layer.